Uninterruptible power supply (UPS) systems are commonly used in installations such as data centers, medical centers and industrial facilities. UPS systems may be used in such installations to provide backup power to maintain operation of computer, medical devices and other critical equipment in event of failure of a primary utility supply. These UPS systems commonly have an “on-line” configuration including a rectifier and inverter coupled by a DC link that is also coupled to a backup power source, such as a battery. Other UPS configurations may also be used, such as standby and line-interactive configurations.
External battery modules (EBMs) may be used to extend the run-time (back-up time) of UPSs and do not typically have any in-built intelligence. In other words, EBMs are generally a chassis with a fixed number of battery packs without any monitoring circuitry. In an EBM having multiple battery packs in multiple slots of the EBM chassis (modular EBM), there currently is no cost-effective way to identify a state of a battery, for example, to identify if a particular battery pack has bad batteries that need to be replaced.
Smart EBMs may be provided by adding monitoring circuits to all the battery packs. However, this is an expensive way addressing this problem. Thus, improved methods of monitoring batteries in an EBM may be desired.